Typical fiber optic connectors require a coupling device which effectively optically couples the fiber optic transmission line with an opto-electronic device (OED). The OED is further electronically coupled to electronic circuits which operate in conjunction with the OED. Often, such electronic circuits, including integrated circuits, are mounted on a printed circuit board or ceramic substrate. To accommodate the use of optical transmission devices in densely packed parallel arrangements of circuit boards, it is commonly required that the fiber optic cable enter the printed circuit board along a path substantially parallel to the board with which it will interface.
A prevalent technology in the optical communications industry is surface emitting and detecting devices. Devices such as vertical cavity surface emitting lasers (VCSELs), surface emitting light emitting diodes as well as most PIN detectors have a photosensitive surface to receive or emit light from or to the top or bottom surface. These devices have certain benefits, and alignment of devices such as these to optical fibers has proved relatively difficult, requiring relatively complicated optical structures and paths to effect the coupling.
Some success has been met in coupling surface emitting and detecting devices through a 90 degree molded optic coupler as is disclosed in U.S. Pat. Nos. 5,515,468 and 5,708,743 to DeAndrea, et al., the entire disclosures of both of which are hereby incorporated herein by reference. This technology makes use of polymer molded integrated light coupling devices suitable for coupling light from an OED to an optical fiber and vice versa, and require the device to be disposed on a different plane than the fiber with the light being communicated there between by a reflective surface. Further examples of such techniques are found in U.S. Pat. Nos. 5,073,003 and 4,904,036 to Clark and Blonder respectively, the disclosures of both of which are hereby incorporated herein by reference.
A certain exemplary transceiver lens body 10 (see FIGS. 1a-1f) is generally consistent with these light-bending techniques and includes a body 12 having a fiber-receiving port 14 abutting an interface surface 16 in a side of the body, a reflective surface 20 for redirecting light traveling along an optical path A substantially perpendicularly to the optical fibers disposed in the port 14, and an array 22 of lenses 24 positioned along the bottom 26 of the body 12 to focus light travelling substantially perpendicularly to the fibers in the port 14 through the reflective surface 20 and between the lenses 24 and the interface surface 16, e.g., into fibers supported in the port and abutting the interface surface 16. Thus, the lens body 10 provides optical paths adapted for optically coupling an OED supported on a substrate with a corresponding fiber supported in the port 14 of the lens body 10. As will be appreciated by those of ordinary skill in the art, such a lens body 10 is suitable for inclusion in various cable assemblies and transceivers, which may be mounted in a variety of host systems including for example, routers, computers, switches, bridges, and I/O cards.
Accordingly, it will be appreciated that alignment of the lens body to the substrate, or more particularly, alignment of the lenses, optical paths and fibers to the OEDs on the substrate, is critical for proper optical coupling between the OEDs and the fibers. Active alignment techniques are sometimes used to align the lens body relative to a substrate supporting OEDs (such as VCSELs or other light sources) emitting or receiving light substantially perpendicularly to a plane of the substrate. In an active alignment technique, the light sources are activated (emitting). A problem with active alignment techniques is that the process requires special imaging equipment and can be expensive, particularly with respect to light bending optical couplings. Various passive alignment techniques may also be used. In one passive alignment technique, an image of the light source itself (e.g., a portion of a VCSEL) may be viewed with the human eye through the reflective surface and lenses, thus eliminating the need for special imaging equipment. However, this method requires additional hardware and fixturing to properly view the alignment features, due to tight spacing constraints in the OED assembly. Additionally, this technique is unsafe in that any accidental activation of the light sources will cause damage to the human eye used during the alignment process, since the optical paths for alignment and communication purposes are identical or parallel and/or the alignment feature is the light source itself (e.g., a VCSEL) and thus the eye is in position to be damaged during visualization for alignment purposes. In yet another passive alignment technique, alignment features are provided on the substrate in the same place as the VCSELs/PINs/OEDs. However, in such an arrangement, the alignment structures of the lens body are in a different plane, parallel to and removed from the plane of the VCSELs/PINs OED's. These alignment features are then viewed through a path external to the reflective surface to eliminate the tight spacing constraints. Though safer in that damage to the human eye is less likely in the event of accidental activation of a light source, this method is unsatisfactory and produces inaccurate results because the difference in depths of field, between the two planes, exceed the capability of typical imaging systems. Therefore, in order to achieve alignment, a fixed external reference point must be introduced to which alignment features must be aligned individually. The end result is that the alignment features and alignment structures would be aligned to each other, but the additional step of having to align each to an external reference point introduces additional inaccuracies.
Therefore, Applicants have identified a need for a lens body for coupling an optical fiber to an OED that allows for safe viewing and accurate alignment of any light sources, without the need for special hardware and/or fixturing, using a passive alignment technique. The present invention fulfills this need among others.